I have been looking at those Icebreaker shirts and I see prices more in the $70 range and also some customer reviews of the shirts not being very durable. I am having trouble pulling the trigger on a $70 shirt that may not handle the wear and tear of a "performance cotton" blend at less than half the price.

The Icebreaker store is 50% off a few times a year. Usually 30% off. I have a plain black one that I only paid $30 for.
Getting the ones that are 87% merino, 13% whatever else wears better than 100% merino. They're pretty durable and can survive a normal washing machine.